TESTING BUTTER 639 



absorbent, extract the fat with anhydrous, alcohol-free ether, receiv- 

 ing the solution in a weighed flask. Evaporate the ether, dry the 

 extract at the temperature of boiling water and weigh at hourly 

 intervals until the weight is constant. 



Fat Determination by Kohman Method. 1 



Kohman recommends the following fat determination in con- 

 nection with the moisture test : 



"The moisture is determined as usual over a small flame in a 

 tall, rather narrow, lipped aluminum beaker with a capacity of about 

 100 cc., using a 10 gram sample. After the beaker is weighed to 

 determine the loss of moisture, it is filled with petroleum ether and 

 the contents are stirred with a glass rod to secure a thorough mix- 

 ture. It is then covered with a watch crystal and allowed to stand 

 two or three minutes for the mixture of curd and salt to settle, 

 when the solvent is gently decanted off without disturbing the sedi- 

 ment. The beaker is then filled with fresh solvent. The curd and 

 salt mixture settles rapidly in the fresh solvent and the liquid can 

 be decanted off after a very short time. By gently heating the 

 beaker now, either on a water bath or a hot plate, or directly over a 

 small flame, but not so rapidly as to cause sputtering, the sediment 

 can be completely freed of petroleum ether by evaporation in a very 

 short time. The per cent of fat is then determined by difference 

 upon reweighing the beaker with its contents. The salt is now in 

 ideal condition to be determined by titration, using a solution of such 

 strength that the number of cc. used represents the per cent of salt. 



Before trying to evaporate the petroleum ether from the mixture 

 of curd and salt, it is well to loosen it from the bottom of the beaker, 

 gently tapping it on the desk in order to lessen the tendency to sput- 

 ter." According to Kohman, this test requires about 15 minutes. 



Fat Determination by Shaw. 2 



"In this test for fat, the salt and part of the curd are first re- 

 moved with hot water, the remaining curd is dissolved in dilute sul- 

 phuric acid, the acid solution is removed from the fat, and the latter 

 weighed. 



1 Kohman, A Rapid and Accurate Method for Butter Analysis, Suitable for 



Factory Control Work. Journal of Ind. and Eng. Chemistry, Vol. 11, No. 1, 1919. 



2 Shaw, A New Method for Determining Fat and Salt in Butter, Especially 



Adapted for Use in Creameries. U. S. Dept. of Agriculture, B. A. I. Circular 



202, 1912. 



